Add google-endpoints to third_party/.

third_party/google-endpoints/Crypto/Cipher/DES3.py

Index: third_party/google-endpoints/Crypto/Cipher/DES3.py
diff --git a/third_party/google-endpoints/Crypto/Cipher/DES3.py b/third_party/google-endpoints/Crypto/Cipher/DES3.py
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+# -*- coding: utf-8 -*-
+#
+#  Cipher/DES3.py : DES3
+#
+# ===================================================================
+# The contents of this file are dedicated to the public domain.  To
+# the extent that dedication to the public domain is not available,
+# everyone is granted a worldwide, perpetual, royalty-free,
+# non-exclusive license to exercise all rights associated with the
+# contents of this file for any purpose whatsoever.
+# No rights are reserved.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+# ===================================================================
+"""Triple DES symmetric cipher
+
+`Triple DES`__ (or TDES or TDEA or 3DES) is a symmetric block cipher standardized by NIST_.
+It has a fixed data block size of 8 bytes. Its keys are 128 (*Option 1*) or 192
+bits (*Option 2*) long.
+However, 1 out of 8 bits is used for redundancy and do not contribute to
+security. The effective key length is respectively 112 or 168 bits.
+
+TDES consists of the concatenation of 3 simple `DES` ciphers.
+
+The plaintext is first DES encrypted with *K1*, then decrypted with *K2*,
+and finally encrypted again with *K3*.  The ciphertext is decrypted in the reverse manner.
+
+The 192 bit key is a bundle of three 64 bit independent subkeys: *K1*, *K2*, and *K3*.
+
+The 128 bit key is split into *K1* and *K2*, whereas *K1=K3*.
+
+It is important that all subkeys are different, otherwise TDES would degrade to
+single `DES`.
+
+TDES is cryptographically secure, even though it is neither as secure nor as fast
+as `AES`.
+
+As an example, encryption can be done as follows:
+
+    >>> from Crypto.Cipher import DES
+    >>> from Crypto import Random
+    >>> from Crypto.Util import Counter
+    >>>
+    >>> key = b'-8B key-'
+    >>> nonce = Random.new().read(DES.block_size/2)
+    >>> ctr = Counter.new(DES.block_size*8/2, prefix=nonce)
+    >>> cipher = DES.new(key, DES.MODE_CTR, counter=ctr)
+    >>> plaintext = b'We are no longer the knights who say ni!'
+    >>> msg = nonce + cipher.encrypt(plaintext)
+
+.. __: http://en.wikipedia.org/wiki/Triple_DES
+.. _NIST: http://csrc.nist.gov/publications/nistpubs/800-67/SP800-67.pdf
+
+:undocumented: __revision__, __package__
+"""
+
+__revision__ = "$Id$"
+
+from Crypto.Cipher import blockalgo
+from Crypto.Cipher import _DES3
+
+class DES3Cipher(blockalgo.BlockAlgo):
+    """TDES cipher object"""
+
+    def __init__(self, key, *args, **kwargs):
+        """Initialize a TDES cipher object
+        
+        See also `new()` at the module level."""
+        blockalgo.BlockAlgo.__init__(self, _DES3, key, *args, **kwargs)
+
+def new(key, *args, **kwargs):
+    """Create a new TDES cipher
+
+    :Parameters:
+      key : byte string
+        The secret key to use in the symmetric cipher.
+        It must be 16 or 24 bytes long. The parity bits will be ignored.
+    :Keywords:
+      mode : a *MODE_** constant
+        The chaining mode to use for encryption or decryption.
+        Default is `MODE_ECB`.
+      IV : byte string
+        The initialization vector to use for encryption or decryption.
+        
+        It is ignored for `MODE_ECB` and `MODE_CTR`.
+
+        For `MODE_OPENPGP`, IV must be `block_size` bytes long for encryption
+        and `block_size` +2 bytes for decryption (in the latter case, it is
+        actually the *encrypted* IV which was prefixed to the ciphertext).
+        It is mandatory.
+       
+        For all other modes, it must be `block_size` bytes longs. It is optional and
+        when not present it will be given a default value of all zeroes.
+      counter : callable
+        (*Only* `MODE_CTR`). A stateful function that returns the next
+        *counter block*, which is a byte string of `block_size` bytes.
+        For better performance, use `Crypto.Util.Counter`.
+      segment_size : integer
+        (*Only* `MODE_CFB`).The number of bits the plaintext and ciphertext
+        are segmented in.
+        It must be a multiple of 8. If 0 or not specified, it will be assumed to be 8.
+
+    :Attention: it is important that all 8 byte subkeys are different,
+      otherwise TDES would degrade to single `DES`.
+    :Return: an `DES3Cipher` object
+    """
+    return DES3Cipher(key, *args, **kwargs)
+
+#: Electronic Code Book (ECB). See `blockalgo.MODE_ECB`.
+MODE_ECB = 1
+#: Cipher-Block Chaining (CBC). See `blockalgo.MODE_CBC`.
+MODE_CBC = 2
+#: Cipher FeedBack (CFB). See `blockalgo.MODE_CFB`.
+MODE_CFB = 3
+#: This mode should not be used.
+MODE_PGP = 4
+#: Output FeedBack (OFB). See `blockalgo.MODE_OFB`.
+MODE_OFB = 5
+#: CounTer Mode (CTR). See `blockalgo.MODE_CTR`.
+MODE_CTR = 6
+#: OpenPGP Mode. See `blockalgo.MODE_OPENPGP`.
+MODE_OPENPGP = 7
+#: Size of a data block (in bytes)
+block_size = 8
+#: Size of a key (in bytes)
+key_size = ( 16, 24 )